Relegation refers to when a team finishes near the bottom of the league table, and are moved down a division. In the Premier League, teams who finish in the bottom three of the 20 teams in the league get moved down (relegated) to the EFL Championship division. This is seen as a big negative for teams and often brings financial losses, with lower divisions not offering as much money to teams. This often also involves teams losing star players to other clubs in higher divisions so they can keep a high salary.
In the Apple TV+ series, Ted Lasso, Premier League side AFC Richmond are at risk of relegation with one game to go that can keep them in the English football top tier. Richmond manager, Ted Lasso, treats football matches as a way to grow his players and staff, not as a be all and end all to win games. This frustrated Coach Beard and Nathan, who said that winning does matter to some people and being relegated wastes all that the team had built. As a result, Ted put Roy on the bench due to his string of bad performances in games in order to give themselves the best chance at winning against Manchester City F.C. and to save the team from relegation.